Unravelling intraplate Cenozoic magmatism in Mongolia: Reflections

from the present-day mantle or a legacy from the past?

Martha Papadopoulou, Tiff Barry, Alex Rutson

School of Geography, Geology and the Environment,

University of Leicester, UK

mp589@le.ac.uk © Authors. All rights reserved

Mesozoic magmatism (220-75Ma) vs…

… Cenozoic magmatism (62Ma-present day)

Existing hypotheses

• Mantle plume (Logatchev, 1984; Zorin & Lepina, 1985; Windley & Allen, 1993)

Yarmolyuk et al., 2015

Existing hypotheses

• Mantle plume

• Lithospheric rifting or extension (Yarmolyuk et al., 1991)

Existing hypotheses

• Mantle plume

• Lithospheric rifting or extension

• Far-field effect of Indo-Asian collision (Khain, 1990)

Togtokh et al., 2018

Existing hypotheses

• Mantle plume

• Lithospheric rifting or extension

• Far-field effect of Indo-Asian collision

• Upwelling due to the Pacific plate subduction (Zhang

et al., 2016, Togtokh et al., 2018)

Togtokh et al., 2018

Existing hypotheses

• Mantle plume

• Lithospheric rifting or extension

• Far-field effect of Indo-Asian collision

• Upwelling due to the Pacific plate subduction

• Delamination of the lithospheric mantle (Windley et al., 2010; Sheldrick et al., 2018)

Testing hypotheses – 1

• Central Mongolia – Hangai Dome and Valley of Lakes

• Criteria:

1. Mesozoic magmatism

2. Cenozoic magmatism

3. Extension

4. Uplift

Testing hypotheses – 2

• South Mongolia – Gobi Altai

• Criteria:

1. Mesozoic magmatism

2. Cenozoic magmatism

3. Extension

4. Uplift

Testing hypotheses – 3

• SE Mongolia – Dariganga

• Criteria:

1. Mesozoic magmatism

2. Cenozoic magmatism

3. Extension

4. Uplift

Valley of Lakes & Hangai Dome

Values for crustal xenoliths: Stosch et al., 1995, Mesozoic Gobi Altai: Sheldrick et al., 2018; Hangai Dome: Barry et al., 2003;

Hunt et al., 2012; Mesozoic rocks: Dash et al., 2015, Sheldrick – unpublished data © Authors. All rights reserved

Gobi Altai

Values for crustal xenoliths: Stosch et al., 1995, Mesozoic Gobi Altai: Sheldrick et al., 2018; Hangai Dome: Barry et al., 2003;

Hunt et al., 2012; Mesozoic rocks: Dash et al., 2015, Sheldrick – unpublished data © Authors. All rights reserved

Dariganga

Values for crustal xenoliths: Stosch et al., 1995, Mesozoic Gobi Altai: Sheldrick et al., 2018; Hangai Dome: Barry et al., 2003;

Hunt et al., 2012; Mesozoic rocks: Dash et al., 2015, Sheldrick – unpublished data © Authors. All rights reserved

Mantle tomography

Regional data model; Reference model: PREM © Authors. All rights reserved

Mantle tomography

Based on averaged global data models; Reference model: PREM © Authors. All rights reserved

Discussion/next steps

• Valley of Lakes: samples trend from lithosphere-like (Mesozoic samples) to asthenosphere-like (Hangai Dome) – may reflect reactivation of Mesozoic melt during influx of new melt in the Cenozoic

• Gobi Altai Mesozoic and Cenozoic samples show similar source compositions – may reflect reactivation during Cenozoic

• Dariganga: modified crustal melts? Or reactivated melts from earlier event?

• Test with AFC and partial melting modelling to identify the individual source components for each volcanic field and their relationship

• Tomography no deep mantle anomalies. Anomalies only at ~100 km depth (base of lithosphere)

Thank you!!!!

Contact me: e-mail mp589@le.ac.uk

@Geochem_Maya